问答题
本题随机产生若干字母(A~Z间),直到出现字母Q停止。
public class java1
public static void main(String[]args)
______;
do
c=(char)( );
System.out.print(c+",");
while( );
【参考答案】
第1处:char c
第2处:(int)(Math.random()*26)+’A’
第3处:c!=’Q’
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本题的功能是用按钮来控制文本框中文本的颜色。窗口中有两个带有文字标题的面板“Sample text”和“Text color control”,窗口的底部还有一个复选按钮“Disable changes”。在“Sample text”面板中有一个带有字符串的文本框,而在“Text color control”面板中有三个按钮“Black”、“Red”和“Green”,并且每个按钮上都有一个对应颜色的圆。单击任意按钮,文本框的文本变成对应的颜色,如果选中“Disable changes”复选框,则三个颜色按钮变为不可用,如果取消选中复选框,则三个按钮变为可用。 import javax.swing.*; import java.awt.*; import java.awt.event.*; public class java3 extends JFrame private JPanel upper,middle,lower; private JTextField text; private JButton black,red,green; private JCheckBox disable; public java3(String titleText) super(titleText); addWindowListener(new WindowAdapter() public void windowClosing(WindowEvent e) System.exit(0); ); upper=new JPanel(); upper.setBorder(BorderFactory.createTitledBorder( Sample text )); Upper.setlayout(new BorderLayout()); text=new JTextField( Change the color of this text ); upper.add(text,BorderLayout,CENTER); middle=new JPanel(); middle.setBorder(BorderFactory.createTitledBorder( Text color control )); middle.setLayout(new FlowLayout(FlowLayout.CENTER)); black=new JButton( Black ,new Colorlcon(Color.black)); black.addActionListener(new ButtonListener(Color.black)); middle.add(black); red=new JButton( Red ,new Colorleon(Color.red)); red.addActionListener(new ButtonListener(Color.red)); middle.add(red); green=new JButton( Green ,new Colorlcon(Color.green)); green.addActionListener(new ButtonListener(Color.green)); middle.add(green); lower=new JPanel(); lower.setLayout(new FlowLayout(FlowLayout.RIGHT)); disable=new JCheckBox( Disable changes ); disable.addhemListener(new ItemListener() public void itemStateChanged(ItemEvent e) boolean enabled =(e.getStateChange() ==ItemEvent.DESELECTED); black.setEnabled(enabled); red.setEnabled(enabled); green.setEnabled(enabled); ); lower.add(disable); Container cp=getContentPane(); cp.add(upper,BorderLayout.NORTH); cp.add(middle,BorderLayout.CENTER); cp.add(lower,BorderLayout.SOUTH); pack(); setVisible(true); class ButtonListener extends ActionListener private Color c; public ButtonListener(Color c) this.c=c; public void actionPerformed(ActionEvent e) text.setForeground(c); class Colorlcon implements Icon private Color c; private static final int DIAMETER=10; public ColorIcon(Color c) c=c; public void paintIcon(Component cp,Graphics g, int x,int y) g.setColor(c); g.fillOval(x,y,DIAMETER,DIAMETER); g.setColor(Color.black); g.drawOval(x,y,DIAMETER,DIAMETER); public int getIconHeight() return DIAMETER; public int getIconWidth() return DIAMETER; public static void main(String[]args) new java3( java3 );
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本题用复选框来控制字体的显示,窗口中有一个标签和两个复选按钮,这两个复选按钮分别对应的字体的两个特点:加粗和倾斜,任意选中一个按钮或两个都选中,标签上的字符串就显示对应的字体。 import java.awt.*; import java.awt.event.*; import javax.swing.*; class CheckBoxFrame extends JFrame implements ActionListener public CheckBoxFrame() setTitle( CheckBoxTest ); setSize(300,200); addWindowListener(new WindowAdapter() public void windowClosing(WindowEvent e) System.exit(0); ); JPanel p=new JPanel(); bold=addCheckBox(p, Bold ); italic=addCheckBox(p, Italic ); getContentPane().add(p, South ); panel=new CheckBoxTestPanel(); getContentPane().add(panel, Center ); public JCheckBox addCheckBox(JPanel p,String name) JCheckBox c=new JCheckBox(name); c.addActionListener( ); p.add(c); return c; public void______ int m=(bold.isSelected()Font.BOLD:0)+(italic.isSelected()Font.ITALIC:0); panel.setFont(m); private CheckBoxTestPanel panel; private JCheckBox bold; private JCheckBox italic; class CheckBoxTestPanel extends JPanel public CheckBoxTestPanel() setFont(Font.PLAIN); public void setFont(int m) setFont(new Font( SansSerif ,m,12)); repaint(); public void paintComponent(Graphics g) super.paintComponent(g); g.drawstring( The quick brown fox jumps over the lazy dog. ,0,50); public class java2 public static void main(String[]args) JFrame frame=new CheckBoxFrame(); frame.show();
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